Field of the Invention
The present invention concerns wireless communications, and more specifically, to methods and apparatuses of detecting the location of a terminal in a multi-node system.
Related Art
The amount of data transferred over a wireless communication network is recently increasing very quickly. One reason may be attributed to the introduction and use of various devices including smartphones or tablet PCs requiring machine-to-machine (M2M) communication and high data transfer. To meet the demand for high data transfer, more attention is drawn to carrier aggregation and cognitive ratio technology that enable efficient use of more frequency bands and multi-antenna technique or multi-base station cooperation technique for boosting data capacity in a limited frequency.
Further, wireless communication networks evolve to have more density of nodes to which uses may have access. Here, the term “nodes” sometimes refers to antennas spaced apart from each other at a certain distance in a distributed antenna system (DAS) but is not limited thereto and may rather have a broader concept. In other words, a node may be a pico cell base station (PeNB), a home base station (HeNB), an RRH (Remote Radio Head), an RRU (Remote Radio Unit), or a relay station. The node may also be referred to as a point.
Such wireless communication system with high node density may show higher system capacity through inter-node cooperation. That is, when nodes are managed by a single control station for their transmission and reception to be operated as if they are a single antenna or antenna group, much better system performance can be achieved rather than when they each serve as an independent base station (BS), advanced BS (ABS), node-B (NB), eNode-B (eNB), or access point (AP). Hereinafter, a wireless communication system including a plurality of nodes is referred to as a multi-node system.
In a multi-node system, a plurality of nodes are distributed, and thus, which node a terminal is in communication with may be critical depending on the location of the terminal. For this, grasping the location of the terminal matters. A method for grasping where a terminal is located is to use a PRS (positioning reference signal) in a conventional wireless communication system. According to existing communication standards in relation with the PRS, a sequence is generated based on a physical cell ID (identifier), and is mapped with a radio resource.
Meanwhile, the existing multi-node systems assume use of one cell ID by multiple nodes. Accordingly, per the existing communication standards, a plurality of nodes should use the same physical cell ID when sending a PRS. In such case, a terminal might not be aware of which node has sent the PRS. Further, a base station may have difficulty in exactly grasping the position of the terminal from a result of measuring the PRS, which is fed back from the terminal.